This looks staged, and i think I have seen this photo before saying it was intentional. It looks like multiple rounds fired with either just the primer or the primer and a touch of powder. I actually had a squib from a factory load while I was firing variable string lengths of two or more as called by a partner. There was a slightly odd sounding 'pop' at one point, followed by a slightly louder than normal gunshot - but with all the other firing going on, sometimes sound plays tricks. The pistol continued to fire just fine, cycled smoothly, etc.
At any rate, I finished out the day and noticed a large bulge in the barrel on disassembly - it looked nothing like the cut barrel in the op. Bulged area was about 1" in length, with the largest diameter near the center of that area. I'm not an engineer, but I'm guessing the bulge was caused by compression of the gasses trapped between the squib bullet and the next good round as it traveled down the barrel. I think the 'pop' was the noise of the lodged round finally being forced out as the pressure behind it increased.
The round in question was UMC, and Remington took care of me quickly and with no questions asked. They took the pistol and checked it for cracks and stress (forget the process name, but it was done with magnetic fields) and replaced the barrel. While they didn't say so, I believe the replacement was match grade. Pistol was more accurate when I got it back.
Kudos to Remington